The present invention relates to a compressor. More particularly, the present invention relates to a piston type compressor that provides a piston ring fitted onto a piston.
A piston type compressor such as a swash plate type compressor generally includes a cylinder block and suction and discharge chambers so as to sandwich a valve plate assembly, and the cylinder block accommodates a piston. By reciprocation of the pistons, fluid in the suction chamber is sucked into the cylinder block, and the fluid sucked in the cylinder block is compressed and discharged to the discharge chamber. Also, to suck the fluid into the cylinder block and compress and discharge the fluid to the discharge chamber efficiently, sealing performance between the pistons and the cylinder block is important. Japanese Unexamined Patent Publication No. 11-294322 discloses a compressor that provides a coating made of fluoro resin on the outer circumferential surface of the pistons and a piston ring fitted onto the pistons. Thereby, sealing performance between the pistons and the cylinder block is ensured.
To achieve higher compression efficiency, sealing performance between the pistons and the piston rings in addition to sealing performance of the pistons and the cylinder block is also required to improve. Alternative refrigerant gas such as carbon dioxide is promoted to be a practical use to deal with environmental problems these days. However, carbon dioxide for using in a compressor as a compressing target requires quite a high compression ratio. Therefore, the above-mentioned requirements for sealing performance have been further increasing these days.
The present invention addresses the above-mentioned problems traceable to a relatively high compression ratio by improving sealing performance between pistons and piston rings.
According to the present invention, a piston type compressor has a housing, a cylinder block and a piston. The cylinder block is fixed to the housing. The piston is accommodated in the cylinder block. A piston ring is provided between the cylinder block and the piston. A sealing coat is made of soft metal, and is provided between the piston ring and the piston.
In the piston type compressor mentioned above, sealing performance between the piston ring and the piston is improved by the sealing coat made of soft metal.
The present invention also provides a method of forming a sealing coat on a surface of a groove on a piston. The method includes forming a coat made of fluoro resin on the outer circumferential surface of the piston, recessing a groove for accommodating a piston ring on the outer circumferential surface of the piston by machining, and immersing the piston in soft metal.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.